1. Field of the Invention
The present invention relates to a roller retainer which is used in a rolling guide apparatus and a roller screw and also which is used to hold rollers rolling through a circulation passage in such a manner that the rollers can be freely rotated and slid.
2. Description of the Related Art
Conventionally, there is known a roller screw structured such that a plurality of rollers are interposed between a screw shaft and a nut member. In case where the screw shaft is rotated with respect to the nut member, the nut member is moved linearly in the axial direction of the screw shaft. In the screw shaft, there is formed a spiral-shaped roller rolling groove. On the other hand, in the nut member, there is formed a roller circulation passage including a spiral-shaped load rolling groove which is so formed as to correspond to the roller rolling groove of the screw shaft. The rollers roll in such a manner that they move along the outer periphery of a screw groove between the screw shaft and nut member, thereby circulating through the roller circulation passage. In such roller screw, the plurality of rollers are, in some cases, arranged parallel in the roller circulation passage in order that the axes of the mutually adjoining rollers can be held almost parallel to each other; and, in other cases, they are cross arranged in such a manner that the axes of the mutually adjoining rollers cross each other.
Generally, in a roller screw in which only the rollers are arranged in the roller circulation passage, the movements of the respective rollers can vary from one another, and the rollers can fall down in a plane including the axes of the rollers and the advancing direction of the rollers to thereby cause a so called skew. Such skew interferes with the lined-up circulation of the rollers. To prevent the skews of the rollers, there is proposed use of a roller retainer which can hold the rollers in such a manner that the rollers can be freely rotated and slid. As shown in FIG. 13, the roller retainer 2 encloses the outer periphery of a roller 1 that is situated on the center line 1a of the roller 1 when the roller 1 is viewed from the side surface thereof, and thus restricts the roller 1 to thereby prevent the roller 1 against skew.
However, in the conventional roller retainers 2, when the rollers 1 are arranged in a crossing manner, the roller retainers 2 are also arranged in a crossing manner that the roller retainers 2 cross each other, which makes it impossible to obtain a large contact area between the roller retainers 2. For this reason, the conventional roller retainers 2 cannot be applied to the rollers 1 which are cross arranged.
Also, since the conventional roller retainer 2 encloses the outer periphery of the roller 1 that is situated on the center line 1a of the roller 1 when the roller 1 is viewed from the side surface thereof, the roller 1 is easy to slip off the roller retainer 2 and the roller retainer 2 is not be able to provide a sufficient force to hold the roller 1, thereby raising a fear that the skew of the roller cannot be controlled.
The present invention aims at eliminating the above drawbacks found in the conventional roller retainer, and therefore an object of the invention is to provide a roller retainer which can be applied to both of cross arranged rollers and parallel arranged rollers and can restrict the rollers more positively in such a manner the skews of the rollers can be controlled, as well as a linear guide apparatus and a roller screw respectively using such roller retainers.
Now, description will be given below of the invention. By the way, for easy understanding of the invention, reference numerals shown in the accompanying drawings are stated herein while putting them in parentheses; however, the invention is not limited to the illustrated embodiments thereof. In attaining the above object, according to the invention, the outer periphery of a roller situated on a diagonal when the roller is viewed from the side surface thereof is enclosed by a roller retainer, and the corner portion and cylindrical portion of the roller are restricted.
In other words, according to a first aspect of the invention, there is provided a roller retainer (11) for holding a roller (9) circulating through a roller circulation passage, wherein the roller retainer (11) encloses the outer periphery of the roller (9) situated on a diagonal (20) when the roller (9) is viewed from the side surface thereof. Here, the roller retainer may hold a plurality of rollers, which respectively circulate through the roller circulation passage, in a series manner, or the roller retainer may hold the plurality of rollers individually.
According to the first aspect of the invention, since the roller retainer encloses the outer periphery of the roller that is situated on the diagonal when the roller is viewed from the side surface thereof, the roller retainer is allowed to keep a constant position whether the rollers are arranged in a parallel manner or in a cross manner and thus the disposition of the roller retainer is free from the influence of the direction of the roller. Therefore, there can be obtained a roller retainer which can be applied not only to a structure in which rollers are parallel arranged but also to a structure in which rollers are cross arranged. Also, because the roller retainer restricts the corner portion of the roller, the roller is difficult to slip off the roller retainer, thereby being able to restrict the roller positively, so that the skew of the roller can be controlled.
Also, according to a second aspect of the invention, in a roller retainer according to the first aspect of the invention, the roller retainer (11) holds individually a plurality of rollers (9) which are respectively allowed to circulate through the roller circulation passage.
In the case of a roller screw, the circulation path of a roller draws a spiral shape. In case where a roller retainer is formed in a band shape so that it can hold a plurality of rollers in a series manner, the roller retainer is spirally twisted and a load is thereby applied to the roller retainer, which raises a fear that the roller retainer can be damaged or broken. However, according to the second aspect of the invention, since the roller retainer holds the plurality of rollers individually, even in case where the circulation path of the roller is formed in a spiral shape, the roller retainer can be prevented against damage or breakage.
Further, according to a third aspect of the invention, in a roller retainer according to the first or second aspect of the invention, the roller retainer (11) is molded with the roller (9) inserted therein. As the molding method, for example, there can be employed a method in which molten resin is injection molded into a metal mold in which the roller has been installed.
According to the third aspect of the invention, a clearance between the roller retainer and roller can be made small to thereby be able to restrict the roller positively.
Also, according to a fourth aspect of the invention, there is provided a roller screw comprising: a track shaft (5) including a spiral-shaped roller rolling groove (5a) having a V-shaped section; a slide member (6) comprising a roller circulation passage including a spiral-shaped load rolling groove (6a) having a V-shaped section and assembled to the track shaft (5) in such a manner that it can be moved with respect to the track shaft (5), the load rolling groove (6a) being so formed as to correspond to the roller rolling groove (5a); a plurality of rollers (9) respectively arranged and stored in the roller circulation passage and allowed to circulate through the roller circulation passage in linking with the relative motion of the slide member (6) with respect to the track shaft (5); and a plurality of retainers (11) for holding the plurality of rollers (9) individually in such a manner that the rollers (9) can be rotated and slid, wherein each of the roller retainers (11) encloses the outer periphery of its associated one of the rollers (9) that is situated on a diagonal (20) when the roller (9) is viewed from the side surface thereof, and also wherein, in at least one of the roller rolling groove (5a) and load rolling groove (6a), there is formed a guide groove (10, 14) for guiding the roller retainer (11).
According to the fourth aspect of the invention, not only there can be obtained the above-mentioned operation effects, but also, since the roller retainer is guided by the guide groove, the fall-down of the roller retainer as well as the skew of the roller can be controlled.
Further, according to a fifth aspect of the invention, there is provided a rolling guide apparatus comprising: a track shaft (31) including a roller rolling groove (31a) having a V-shaped section; a slide member (32) comprising a roller circulation passage including a load rolling groove (32a) having a V-shaped section and assembled to the track shaft (31) in such a manner that it can be moved with respect to the track shaft (31), the load rolling groove (32a) being so formed as to correspond to the roller rolling groove (31a); a plurality of rollers (9) respectively arranged and stored in the roller circulation passage and allowed to circulate through the roller circulation passage in linking with the relative motion of the slide member (32) with respect to the track shaft (31); and, a plurality of retainers (11) for holding the plurality of rollers (9) individually in such a manner that the rollers can be rotated and slid, wherein each of the roller retainers (11) encloses the outer periphery of its associated one of the rollers (9) that is situated on a diagonal (20) when the roller (9) is viewed from the side surface thereof, and also wherein, in at least one of the roller rolling groove (31a) and load rolling groove (32a), there is formed a guide groove (38) for guiding the roller retainer (11).
According to the fifth aspect of the invention, not only there can be obtained the above-mentioned operation effects, but also, since the roller retainer is guided by the guide groove, the fall-down of the roller retainer as well as the skew of the roller can be controlled.